RE: [Exim] Exim as front door to Exchange

I have entered the proper information on the manualroute router. To
test it, I am telnetting into the Exim box on port 25 and trying to "send"
an e-mail this way. It does the HELO and MAIL FROM fine. But then I
enter RCPT TO: user@???. I get a message:

451 Temporary local problem - please try later.

What is causing this? Is there something wrong with how I have
entered the manual route info?

Chris